Refactor PR rust-lang#119397

Co-authored-by: León Orell Valerian Liehr <me@fmease.dev>

compiler/rustc_parse/src/errors.rs

@@ -3,7 +3,7 @@ use std::borrow::Cow;
 use rustc_ast::token::Token;
 use rustc_ast::{Path, Visibility};
 use rustc_errors::{
-    AddToDiagnostic, Applicability, DiagCtxt, DiagnosticBuilder, IntoDiagnostic, Level, MultiSpan,
+    AddToDiagnostic, Applicability, DiagCtxt, DiagnosticBuilder, IntoDiagnostic, Level,
     SubdiagnosticMessage,
 };
 use rustc_macros::{Diagnostic, Subdiagnostic};
@@ -2382,7 +2382,7 @@ pub(crate) struct ExpectedCommaAfterPatternField {
 #[diag(parse_unexpected_paren_in_range_pat)]
 pub(crate) struct UnexpectedParenInRangePat {
     #[primary_span]
-    pub span: MultiSpan,
+    pub span: Vec<Span>,
     #[subdiagnostic]
     pub sugg: UnexpectedParenInRangePatSugg,
 }

compiler/rustc_parse/src/parser/pat.rs

@@ -1,14 +1,14 @@
 use super::{ForceCollect, Parser, PathStyle, TrailingToken};
 use crate::errors::{
-    AmbiguousRangePattern, BoxNotPat, DotDotDotForRemainingFields,
-    DotDotDotRangeToPatternNotAllowed, DotDotDotRestPattern, EnumPatternInsteadOfIdentifier,
-    ExpectedBindingLeftOfAt, ExpectedCommaAfterPatternField,
-    GenericArgsInPatRequireTurbofishSyntax, InclusiveRangeExtraEquals, InclusiveRangeMatchArrow,
-    InclusiveRangeNoEnd, InvalidMutInPattern, PatternOnWrongSideOfAt, RefMutOrderIncorrect,
-    RemoveLet, RepeatedMutInPattern, SwitchRefBoxOrder, TopLevelOrPatternNotAllowed,
-    TopLevelOrPatternNotAllowedSugg, TrailingVertNotAllowed, UnexpectedLifetimeInPattern,
-    UnexpectedParenInRangePat, UnexpectedParenInRangePatSugg,
-    UnexpectedVertVertBeforeFunctionParam, UnexpectedVertVertInPattern,
+    self, AmbiguousRangePattern, DotDotDotForRemainingFields, DotDotDotRangeToPatternNotAllowed,
+    DotDotDotRestPattern, EnumPatternInsteadOfIdentifier, ExpectedBindingLeftOfAt,
+    ExpectedCommaAfterPatternField, GenericArgsInPatRequireTurbofishSyntax,
+    InclusiveRangeExtraEquals, InclusiveRangeMatchArrow, InclusiveRangeNoEnd, InvalidMutInPattern,
+    PatternOnWrongSideOfAt, RefMutOrderIncorrect, RemoveLet, RepeatedMutInPattern,
+    SwitchRefBoxOrder, TopLevelOrPatternNotAllowed, TopLevelOrPatternNotAllowedSugg,
+    TrailingVertNotAllowed, UnexpectedLifetimeInPattern, UnexpectedParenInRangePat,
+    UnexpectedParenInRangePatSugg, UnexpectedVertVertBeforeFunctionParam,
+    UnexpectedVertVertInPattern,
 };
 use crate::{maybe_recover_from_interpolated_ty_qpath, maybe_whole};
 use rustc_ast::mut_visit::{noop_visit_pat, MutVisitor};
@@ -19,7 +19,7 @@ use rustc_ast::{
     PatField, PatFieldsRest, PatKind, Path, QSelf, RangeEnd, RangeSyntax,
 };
 use rustc_ast_pretty::pprust;
-use rustc_errors::{Applicability, DiagnosticBuilder, MultiSpan, PResult};
+use rustc_errors::{Applicability, DiagnosticBuilder, PResult};
 use rustc_session::errors::ExprParenthesesNeeded;
 use rustc_span::source_map::{respan, Spanned};
 use rustc_span::symbol::{kw, sym, Ident};
@@ -604,7 +604,7 @@ impl<'a> Parser<'a> {
                         && let Some(form) = self.parse_range_end() =>
                 {
                     self.dcx().emit_err(UnexpectedParenInRangePat {
-                        span: MultiSpan::from_spans(vec![open_paren, close_paren]),
+                        span: vec![open_paren, close_paren],
                         sugg: UnexpectedParenInRangePatSugg {
                             start_span: open_paren,
                             end_span: close_paren,
@@ -745,24 +745,53 @@ impl<'a> Parser<'a> {
         Some(respan(self.prev_token.span, re))
     }
 
+    /// Parse using `f(self)`, but may eat parentheses before and after calling `f(self)` (and emit an error in this case.)
+    /// Can trivially be generalized for other [`Delimiter`] and errors other than [`UnexpectedParenInRangePat`] if desired.
+    fn maybe_recover_paren_around_range_bound<T, F>(&mut self, f: F) -> PResult<'a, T>
+    where
+        F: Fn(&mut Parser<'a>) -> PResult<'a, T>,
+    {
+        // recover from leading `(`
+        if self.may_recover() && self.token.kind == token::OpenDelim(Delimiter::Parenthesis) {
+            let mut snapshot = self.create_snapshot_for_diagnostic();
+            snapshot.bump();
+
+            let open_paren = snapshot.prev_token.span;
+            let parsed = f(&mut *snapshot)?;
+
+            // check for trailing `)`
+            if snapshot.eat_noexpect(&token::CloseDelim(Delimiter::Parenthesis)) {
+                self.restore_snapshot(snapshot);
+
+                self.dcx().emit_err(UnexpectedParenInRangePat {
+                    span: vec![open_paren, self.prev_token.span],
+                    sugg: UnexpectedParenInRangePatSugg {
+                        start_span: open_paren,
+                        end_span: self.prev_token.span,
+                    },
+                });
+
+                Ok(parsed)
+            } else {
+                // `f(snapshot)` parsed something but we're now missing a `)`,
+                // so just abort the recovery attempt
+                f(self)
+            }
+        } else {
+            f(self)
+        }
+    }
+
     /// Parse a range pattern `$begin $form $end?` where `$form = ".." | "..." | "..=" ;`.
     /// `$begin $form` has already been parsed.
     fn parse_pat_range_begin_with(
         &mut self,
         begin: P<Expr>,
         re: Spanned<RangeEnd>,
     ) -> PResult<'a, PatKind> {
-        // recover from `(`
-        let open_paren = (self.may_recover()
-            && self.token.kind == token::OpenDelim(Delimiter::Parenthesis))
-        .then(|| {
-            self.bump();
-            self.prev_token.span
-        });
-
         let end = if self.is_pat_range_end_start(0) {
             // Parsing e.g. `X..=Y`.
-            Some(self.parse_pat_range_end()?)
+            Some(self.maybe_recover_paren_around_range_bound(|this| this.parse_pat_range_end())?)
         } else {
             // Parsing e.g. `X..`.
             if let RangeEnd::Included(_) = re.node {
@@ -772,18 +801,6 @@ impl<'a> Parser<'a> {
             None
         };
 
-        if let Some(span) = open_paren {
-            self.expect(&token::CloseDelim(Delimiter::Parenthesis))?;
-
-            self.dcx().emit_err(UnexpectedParenInRangePat {
-                span: MultiSpan::from_spans(vec![span, self.prev_token.span]),
-                sugg: UnexpectedParenInRangePatSugg {
-                    start_span: span,
-                    end_span: self.prev_token.span,
-                },
-            });
-        }
-
         Ok(PatKind::Range(Some(begin), end, re))
     }
 
@@ -823,32 +840,13 @@ impl<'a> Parser<'a> {
     /// The form `...X` is prohibited to reduce confusion with the potential
     /// expression syntax `...expr` for splatting in expressions.
     fn parse_pat_range_to(&mut self, mut re: Spanned<RangeEnd>) -> PResult<'a, PatKind> {
-        // recover from `(`
-        let open_paren = (self.may_recover()
-            && self.token.kind == token::OpenDelim(Delimiter::Parenthesis))
-        .then(|| {
-            self.bump();
-            self.prev_token.span
-        });
+        let end = self.maybe_recover_paren_around_range_bound(|that| that.parse_pat_range_end())?;
 
-        let end = self.parse_pat_range_end()?;
         if let RangeEnd::Included(syn @ RangeSyntax::DotDotDot) = &mut re.node {
             *syn = RangeSyntax::DotDotEq;
             self.dcx().emit_err(DotDotDotRangeToPatternNotAllowed { span: re.span });
         }
 
-        if let Some(span) = open_paren {
-            self.expect(&token::CloseDelim(Delimiter::Parenthesis))?;
-
-            self.dcx().emit_err(UnexpectedParenInRangePat {
-                span: MultiSpan::from_spans(vec![span, self.prev_token.span]),
-                sugg: UnexpectedParenInRangePatSugg {
-                    start_span: span,
-                    end_span: self.prev_token.span,
-                },
-            });
-        }
-
         Ok(PatKind::Range(None, Some(end), re))
     }
 
@@ -1013,7 +1011,7 @@ impl<'a> Parser<'a> {
 
         if self.isnt_pattern_start() {
             let descr = super::token_descr(&self.token);
-            self.dcx().emit_err(BoxNotPat {
+            self.dcx().emit_err(errors::BoxNotPat {
                 span: self.token.span,
                 kw: box_span,
                 lo: box_span.shrink_to_lo(),

tests/ui/half-open-range-patterns/range_pat_interactions2.rs

@@ -8,7 +8,7 @@ fn main() {
     for x in -9 + 1..=(9 - 2) {
         match x as i32 {
             0..=(5+1) => errors_only.push(x),
-            //~^ error: expected `)`, found `+`
+            //~^ error: unexpected token: `(`
             1 | -3..0 => first_or.push(x),
             y @ (0..5 | 6) => or_two.push(y),
             y @ 0..const { 5 + 1 } => assert_eq!(y, 5),

tests/ui/half-open-range-patterns/range_pat_interactions2.stderr

@@ -1,8 +1,8 @@
-error: expected `)`, found `+`
-  --> $DIR/range_pat_interactions2.rs:10:19
+error: unexpected token: `(`
+  --> $DIR/range_pat_interactions2.rs:10:17
    |
 LL |             0..=(5+1) => errors_only.push(x),
-   |                   ^ expected `)`
+   |                 ^
 
 error: aborting due to 1 previous error